Self-centering phakic intraocular lens

ABSTRACT

The present application discloses a phakic intraocular lens (IOL) for the correction of visual disorders such as myopia, hyperopia, astigmatism and presbyopia. The lens is made from a biocompatible, elastomeric material such as silicone. The lens further includes one or more annular surfaces that protrude from the anterior surface of the lens or surrounds the lens such that when placed in the eye, it makes contact with the iris. As the iris dilates and constricts, the contact with the iris places a centering force on the implanted lens. The lens is not in contact with the natural lens of the eye and floats in the posterior chamber without insult or abrasion to surrounding tissue.

This is a continuation patent application based on U.S. patentapplication Ser. No. 08/955,917, Valunin, et al., filed Oct. 22, 1997,now U.S. Pat. No. 6,015,435, issued Jan. 18, 2000, which claims benefitfrom U.S. Provisional Patent Application No. 60/029,103, filed Oct. 24,1996, and U.S. Provisional Patent Application No. 60/029,341, filed Oct.31, 1996.

TECHNICAL FIELD

The present invention relates to an intraocular lens for the correctionof visual disorders.

BACKGROUND OF THE INVENTION

According to “Intraocular Lenses,” authored by Dr. David J. Apple,published by Williams and Wilkins, 1989, evidence of the concept ofintraocular lenses dates back at least two centuries. An 18th centuryoculist named Tadini proposed the idea of a lens implant and evenattempted the development of one. The first recorded implant was byCasaamata around 1795, which failed due to inadequate fixation of theimplant to the surface of the eye. The first successful series ofimplants is credited to Dr. Harold Ridley of London. Ridley observedfragments of an acrylic plastic material used in World War II fightercanopies lodged in the eyes of fighter pilots he treated. Finding nobiologic reaction, he chose to use this rigid material for his firstintraocular lens implants. A clinical quality version of the material,polymethylmethacrylate (PMMA), more commonly known as Plexiglass, wasfabricated by Rayners of London into the first synthetic intraocularlenses (IOL).

Inflammation was commonly observed as a major complication when theseearly lenses were used. Ridley, however, considered moderatepostoperative inflammation to be beneficial because it created adhesionsto affix the lens implant. Factors which contributed to the developmentof postoperative inflammation included residues on or in the lenses ofthe sterilizing compounds, disinfectants, polishing residues on or inthe lenses of the sterilizing compounds, disinfectants, polishingcompounds, or additives which were added to control polymerization, aswell as rough or sharp edges, holes, or ridges on the intraocular lensitself. Poor lens design suppressed the growth of IOL's until the designimproved and the market grew rapidly in the 1980's.

According to “Intraocular Lens Implantation” by Dr. Emanuel S. Rosen, etal., published by The C. V. Mosby Company, 1984, intraocular lensimplant procedures are used primarily for the correction of cataracts, adisease that affects the clarity of the natural lens. For the lens ofthe eye to remain functional it must maintain its shape andtransparency. The embryonic lens is formed by layers of epithelial cellsthat elongate, form a crystalline structure and become optically clear.This formation process slows down but continues throughout life. Theprocess can be upset by a number of environmental insults including oldage, chemical contamination or physical injury. Any of these can triggerthe formation of crystalline structures that occur within the lensitself. The newly formed crystalline structures scatter light anddestroy the transparency of the lens. In cataract treatment, the IOLreplaces the natural lens.

Intraocular corrective lenses for the treatment of refractive errors isa logical evolution of the cataract replacement IOL technology.Corrective lenses (eyeglasses, contact lenses) have been the mainstayfor the correction of visual acuity defects. Myopia (nearsightedness),hyperopia (farsightedness), astigmatism and presbyopia (loss of nearvision due to factors such as natural lens inflexibility) can all betreated with eyeglasses and contact lenses. Phakic lenses are ones whichare used in combination with, rather than in place of, the natural lensin the eye. However, the use of phakic IOLs has generally beenunsuccessful due to design related issues that cause insult to thenatural lens resulting in such complications as cataracts or abrasion ofsurrounding tissue.

Refractive surgery is an alternative for treatment of certain types ofvisual acuity defects. Radial keratotomy (RK) and photorefractive radialkeratectomy (PRK) are useful in treating mild to moderate myopia of 6diopters or less and have shown limited success in treating astigmatism.The effectiveness of these procedures is less predictable in patientswith higher degrees of myopia and cannot be used to treat hyperopia orpresbyopia. Neither procedure is without significant postoperativeevents. The hyperopic shift and corneal instability following radialkeratotomy and the high incidence of postoperative corneal haze, halosand starbursts with PRK are well documented in the literature.Additionally, both procedures produce overcorrection (hyperopia) andundercorrection (residual myopia) in a significant number of patients.Laser intrastromal in situ keratomilieusis (LASIK) is a new refractivesurgery procedure that, in an experienced surgeon's hands, can treatboth low and high degrees of myopia, hyperopia and astigmatism.Preliminary data indicate that LASIK produces few postoperative visualevents, postoperative vision stabilizes rapidly compared to RK and PRK,and LASIK does not appear to produce any residual weakening inendothelial structure.

The phakic IOL fills the gaps in refractive surgery treatment modalitiesfor visual acuity defects of all types, including astigmatism and,potentially, presbyopia, assuming that the shortcomings, discussedabove, can be dealt with effectively. Such lenses are indicated for anylevel of myopia or hyperopia, including correction beyond 6 diopters.

The basic concept of phakic IOLs was disclosed in U.S. Pat. No.4,585,456, Blackmore, issued Apr. 29, 1986. Blackmore describes a phakiclens which is placed on the surface of the natural lens and centered bybeing held in the ciliary sulcus. This approach failed to provide safeand effective treatment due to such complications as insult to thenatural lens causing cataracts, abrasion of the pigment of the iriscausing angle closure glaucoma and pupilary block glaucoma caused byblocking the flow of the eye's aqueous fluid through the pupil. Fixationof the lens using the interaction of the haptics and the ends of theciliary sulcus requires proper measurement of the eye and selection ofthe proper haptic size (diagonal dimension across the lens and haptic).Improper haptic size can result in decentration of the implanted lenswhich leads to improper vision. See also, Mazzocco, et al., Soft ImplantLenses in Cataract Surgery, Slack, Inc., 1986, p. 93, Model E (a phakiclens fitting in the ciliary sulcus). Several other corrective lensimplants having stiffened or rigid haptics, such as those described inU.S. Pat. No. 5,258,025, Fedorov, et al., issued Nov. 2, 1993, and U.S.Pat. No. 5,078,742, Dahan, issued Jan. 7, 1992, can result in similarcomplications. These complications are documented by Fechner, et al., inthe Journal of Cataract and Refractive Surgery, March, 1996, vol. 22,pp. 178-81. Fechner also makes the observation that a cataract can formwhere the intraocular lens is in contact with the natural lens.Sustained contact between the implanted lens and natural lens can insultthe natural lens by starving it of oxygen or nutrients provided in theaqueous fluid of the eye resulting in formation of a cataract. See also,U.S. Pat. No. 4,769,035, Kelman, issued Sep. 6, 1988, which discloses aphakic intraocular lens which sits directly on the anterior surface ofthe natural lens.

PCT/SU88/00180, assigned to Mikrokhirurgiya Glaza, published Apr. 21,1993, discloses an anterior chamber lens that also has proven to resultin significant complications when used. This lens has a means for iriscentration that requires the lens to protrude into the anterior chamber;a spool-shaped surface on the lens restricts the movement of the iris.This concept also limits the optical diameter of the lens. The designplaces all or part of the lens surface in the anterior chamber of theeye and the edges of the spool scatter light creating haloes in thepatients vision even during periods of bright ambient light. Also,restricting the movement of the iris results in pigment abrasions andpotential trauma to the iris. The maximum diameter or diagonal dimensionmeasured across the optic and haptics is small (less than 10.5 mm)because it is not necessary for the haptics to be centered by theciliary sulcus or the ciliary zonules since the spool-shaped edges ofthe optic body are centered in the pupil of the eye by the iris.

A corrective lens that sits on the natural crystalline lens and uses thecurvature of the natural lens to center the optic body is disclosed inU.S. Pat. No. 5,480,428, Fedorov et al., issued Jan. 2, 1996. This lensis made from inflexible materials and requires surgical insertionwithout substantial deformation of the haptic or the optic bodies, thusrequiring an incision and suturing to close it. The approach requires aport or hole in the optic body to allow flow of the eye's aqueous fluid.Surgeons have overcome complications related to blocking the pupil bycreating a hole in the iris (an iridotomy) to permit the natural flow ofthe eye's aqueous fluid from the posterior chamber to the anteriorchamber of the eye.

It would be highly desirable to develop a phakic intraocular lens whichdid not have the problems associated with the prior art lenses. Thepresent invention overcomes these problems by:

(1) allowing the lens to float freely in the aqueous solution of theeye's posterior chamber;

(2) providing haptics that can move and flex with the anatomy of theeye;

(3) using a self-centration means that does not abrade or restrict themovement of the iris;

(4) providing haptic bodies in combination with the optic body thatcapture the natural flow of the aqueous fluid of the eye to create afluid layer between the implanted lens and the natural lens; and

(5) assisting the circulation of the aqueous fluid of the eye betweenthe natural lens and the implant by utilizing the movement of the iris.

SUMMARY OF THE INVENTION

The present invention is a phakic, intraocular corrective lens for thecorrection of visual disorders such as myopia, hyperopia, astigmatismand presbyopia. The invention comprises an optical body and one or morehaptic bodies. The optical body has a lens for the refraction of lightat an appropriate optical power to correct a visual disorder. Therefractive lens can be negative or positive. The haptic bodies are ofsuch size and shape that they cannot contact the outermost circumferenceof the ciliary sulcus at the same time (i.e., the lens is not held inplace at the ciliary sulcus by the haptic bodies).

The invention is made of a biocompatible, elastomeric material, such assilicone, with a very smooth surface that will not abrade or insult theeye or provide areas where leukocytes and other deposits can collect.The invention may also be made of polymethylmethacrylate,polyhydroxyethylmethacrylate, collagen/acrylic blends and othermaterials which may be hydrophobic, hydrophilic or gas permeable. Theimplanted lens floats in the posterior chamber of the eye withouttouching the natural lens, permitting the implanted lens to move whenvery small forces are applied to it.

The haptic body(ies) included in the present invention are generallynonplanar with substantially uniform thickness and a shape thatapproximates the curvature of the natural lens or are substantiallyspherical. The haptic body(ies) assure that the lens cannot be grosslydecentered in the pupil of the eye by making contact with the peripheryof the posterior chamber in the area of the ciliary sulcus if suchdecentration occurs. The haptic(s) is preferably flexible in thedirection of the optical axis of the lens so that it will follow thechanging radius of the natural lens as the eye accommodates to focus onnear or far objects.

The lens of the present invention further includes one or more annularsurfaces that protrude from the anterior surface of the lens such thatthe annular surface is in the path of the iris as it dilates andconstricts to adjust the aperture or pupil of the eye for variations inambient light. Contact by the moving iris places a centering force onthe protruding annular surface(s) to move and maintain the lens centeredin the pupil of the eye. When the lens is centered, and as the iriscontinues to constrict, the protruding annular surface(s) is shaped soas not to prevent movement of the iris but rather to allow it to slideover the protruding surface. The protruding surface(s) is contoured,radiused, or beveled to assure that it does not abrade the iris as thissliding takes place. The protruding surface(s) can either be part of theoptical body or can be a separate portion of the lens. The surface(s)can be parallel to the optical axis of the eye or ramped to assure thatthe iris can slide up (in the anterior direction) and over the opticalbody of the lens.

The annular protruding surface(s) described above must be of such size,shape and location that its entire surface is within the pupil of theeye when dilated at its maximum aperture. The maximum aperture isachieved in the dark, each night as the patient sleeps, or when dilationis achieved by medication. If the lens becomes decentered beyond themaximum aperture of the pupil, the protruding annular surface will actto decenter the lens rather than to center it. Therefore, to assure theprotruding annular surface is appropriately centered, the haptic body(s)reaches into the periphery of the posterior chamber of the eye toprevent gross decentration. A similar action occurs with positive lenseswhere the convex anterior surface of the lens itself protrudes toreceive the centering force applied by the iris as it constricts.

The constricting and dilating action of the iris acts on the protrudingannular surfaces to move the optic and haptic bodies of the lens tocreate or assist in the flow and circulation of the eye's surroundingaqueous fluid such that oxygen and nutrients in the said fluid reach thenatural lens.

There is great utility and commercial value for corrective lenses thatare implantable in the posterior chamber of the eye to correct visualacuity defects, but the complications which accompany the use of suchdevices have prevented past attempts from being successful. The presentinvention overcomes these complications by permitting the lens to floatfreely in the aqueous solution of the eye rather than being held inplace by the haptics or other fixation methods such as by contactbetween the posterior of the lens and the curvature of the natural lensor fixation in the ciliary sulcus. A free floating, implanted lens willmaintain a layer of aqueous fluid between it and the natural lens bycapturing the natural flow of the aqueous fluid of the eye to bias theimplanted lens away from the natural lens (i.e., unlike many prior artlenses, the lens of the present invention does not rest directly on thenatural lens). The low frictional force created by allowing the lens tofloat freely permits lens centering forces to be applied to the lens bythe iris via the protruding annular surfaces described. The presentinvention allows the lens to be self-centered rather than requiring thatit be held in place by spring loaded haptics, flexible haptics,stiffened haptics, rigid haptics, by adhering to the natural lens orother structures of the eye, or by other fixation methods. The netresult is a phakic intraocular lens which provides optical correctionwithout damaging the delicate structures of the eye.

Other objects and advantages of the invention will become more apparentfrom the following specification taken in conjunction with the figuresherein. These figures are intended to be exemplary and not limiting ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of the eye showing one embodiment ofthe lens of the present invention (11) positioned in the posteriorchamber of the eye (5). The ciliary sulcus (2) and the zonule fibers (3)are also shown. The optical body (12) and the haptic bodies (13) are notin constant contact with the natural lens (1). Contact with the zonules(3) or ciliary sulcus (2) can occur dependent upon the size or anatomyof the eye in relation to the implanted lens. The lens is held incontact with the iris (4) by the flow of the aqueous solution of the eyethat naturally flows through the zonule fibers (3) into the posteriorchamber of the eye (5). Continuity of flow into the anterior chamber ofthe eye (6) is maintained by an iridotomy (surgical opening in theiris).

FIGS. 1a and 1 b are cross-sectional views of two basic embodiments ofthe present invention. FIG. 3a is the top view of the lens whichcorresponds to the cross-section in FIG. 1a, and FIG. 3b is the top viewof the lens which corresponds to the cross-section in FIG. 1b. FIG. 1ais a cross-sectional view of a positive corrective lens (11) with anoptical body (12) and two haptic bodies (13) having thin andsubstantially uniform thickness (129), where the optical body comprisesa convex anterior surface (14) and a concave posterior surface (15) thatis a continuation of the posterior surface of the haptic bodies (16).FIG. 1b shows a similar cross-sectional view of a negative correctivelens (17) with an optical body (12) and two haptic bodies (13) where theoptical body comprises a concave anterior surface (120) and a concaveposterior surface (121) that is a continuation of the posterior surfaceof the haptic bodies (122). The negative lens in FIG. 1b has an annularprotruding surface (43) where the iris may place a centering force onthe lens. Likewise, the positive lens of FIG. 1a has an annularperipheral area (protruding surface) of the lens (43) that issufficiently steep and protrudes into the path of the iris such that theiris may place a centering force on the lens as it constricts and slidesup and over the convex anterior surface (14). Both lenses have anoptical axis (128).

FIGS. 1c and 1 d show cross-sectional views of two other embodiments ofthe present invention. FIG. 1c shows a positive lens (124 c) and FIG. 1dshows a negative lens (124 d) with optical body (125) and haptic bodies(126) having a posterior concave surface (127) such that the radius ofcurvature of the lens posterior concave surface is less than the radiusof curvature of the posterior surface (129) of the two haptic bodies(126). Annular protruding surface (43) shows another potentialembodiment of this invention wherein a ramped surface is provided toassure there is no trauma to the iris as it contacts the surface andslides over it.

FIGS. 1e and 1 f show how the smaller radius of the optical body (125)in FIGS. 1c & 1 d) (compared to the haptic radius) assures that as thehaptic flexes to conform to the changing radius of curvature of thenatural lens (131), the probability of contact with the natural lens atits apex (148) is reduced. FIG. 1e shows the curvature of the naturallens (131) prior to accommodation and FIG. 1f shows the curvature of thenatural lens (131) during accommodation where it is steeper than thecorresponding surface shown in FIG. 1e.

FIG. 1g shows the condition where the radius of the posterior surface(132) is larger than the radius of curvature of the posterior surface ofthe optical body (133) shown in FIG. 1e. The natural lens (131) hascurved during accommodation and the haptic (134) has flexed to followthe changing curvature. This potentially creates a contact point (148)which can cause injury to the natural lens.

FIG. 2a shows a cross-sectional view of another embodiment of thepresent invention (20) where the optical body (22) has an anteriorsurface (23) which has two annular steps (21) to reduce the thickness ofthe lens. The steps (21) comprise annular, anterior surfaces (24) eachof which is a continuation of the anterior surface (23) and annularprotruding surfaces (43) to receive centering forces from the ins. FIG.3f is the top view of the lens which corresponds to the cross-section inFIG. 2a.

FIG. 2b is a cross-sectional view of another embodiment of the invention(20 b) where there is only one step (21) in the optical body (22)creating one annular surface (24) which is a continuation of theanterior surface (23) of the optical body (22).

FIG. 2c is a cross-sectional view (with haptic bodies cut away) of theembodiment of the present invention where the concept of steppedsurfaces is applied to a positive lens and shows the refractivecharacteristics of the lens. Ray (26) which is parallel to the opticalaxis of the lens (28) refracts through the inner annular lens surface(23) of the optical body (22) and intersects the optical axis (28) atthe focal point (27). Ray (29) which is parallel to the optical axis(28) refracts through the outer annular surface (210) of the opticalbody (12) of the lens and also intersects the optical axis (28) at thesame focal point (27). All rays refracted through both annular anteriorsurfaces (23 and 210) will create a single image and these two surfaceswill work as a single optical surface with reduced lens thickness.However, parallel ray (211) represents light passing through theradiused, chamfered, or sloped protruding surface (25) between theannular surfaces (23 and 210) which will not be refracted properly andwill exit from the lens as scattered light. The optical body (22) has anannular peripheral area (212 and 210) that is sufficiently steep andprotrudes into the path of the iris such that the iris will place acentering force on the lens as it constricts.

FIGS. 3a through 3 g show several embodiments of the haptic body whichmay be used in the present invention. FIG. 3a shows an implantable lens(31) with an optical body (12) and two haptic bodies (13) where theoptical body has a tangent point or tangent area (34) with the edge ofthe lens and/or with the annular protruding surface (43 in FIGS. 1a &b). FIG. 3b shows an implantable lens (35) with an optical body (36) anda haptic body (37) where the optical body and annular protrudingsurface(s) (43) are within the edges of the haptic body (37). FIG. 3cshows a similar embodiment with concave cut outs (38) on the short sidesof the haptic (39). FIG. 3d and 3 e show other haptic (310) placementsand designs. FIG. 3f shows a top view of the stepped lens configurationfrom FIG. 2a. FIG. 3g shows the annular protruding surfaces as partialsegments (311); this represents an embodiment where the width of thelens (81) is reduced by truncating a portion of the optical body tofacilitate insertion through a small incision in the eye. As can beseen, the haptic bodies are attached to the optical body and extendoutward therefrom in at least two generally opposite directions (i.e.,bilaterally). These embodiments are intended to be representativeexamples of the many haptic designs which may be used in the intraocularlens of the present invention.

FIG. 4a shows a cross-sectional view of the lens (41) in relationship tothe iris of the eye (42) as it touches the protruding annular surface(43) and, more particularly, the radiused comer (44) between theprotruding annular surface (43) and the anterior surface (45) of theoptical body (46).

FIG. 4b shows a cross-sectional view of the lens (41) in relationship tothe iris of the eye (42) after it has constricted to its constricteddiameter (47), sliding over the protruding annular surfaces (43)allowing the iris (42) to ride over the optical body (46) whilemaintaining contact with the protruding annular surfaces (43) and, moreparticularly, the radiused comers (44) of the lens.

FIG. 4c shows a cross-sectional view of the lens (41) in relationship tothe iris of the eye (42) and the area of the ciliary sulcus (48). Whenthe iris (42) is fully dilated, the lens (41) is allowed to move. Therange of motion of the lens (41) is determined by the relationshipbetween the haptic diameter or diagonal dimension (L), the diameter ofthe eye at the ciliary sulcus (C), the fully dilated diameter of thepatient's pupil (P), and the diameter of the annular protrudingsurface(s) (B).

FIG. 5 shows an isometric view of an embodiment of the lens (51) wherethe anterior surface (52) of the lens (51) is toroidal shaped to correctastigmatism. Radius (R1) is larger than radius (R2) and a continuouslysmooth surface is generated between the radii (R1 and R2).

FIG. 6 shows a cross-sectional view of another embodiment of the lens(61) with an optical body (62) where the anterior surface (63) isaspherical to increase the visual acuity provided to the patient whilemaintaining the same optical power of the lens (61) as compared to aspherical surface (64) depicted by a dashed line.

FIG. 7 shows a cross-sectional view of another embodiment of the presentinvention (71), the optical body (72) having a posterior concave surface(75) and haptic bodies (73) having a posterior concave surface (76) suchthat the two concave surfaces are stepped and connected by transitionalsurface(s) (77). Also shown is the curvature of the natural lens (78).Said step (77) between the posterior concave surfaces (75 & 76) createsa larger gap (79) at the haptic bodies (73) than the gap (710) at theoptic body (72). This larger gap (79) permits increased fluid flow suchthat a greater amount of oxygen and nutrients reaches the natural lens.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For a better understanding of the invention, the following descriptionof the preferred embodiment should be taken in conjunction with theabove-described drawings:

Particularly preferred embodiments of the present invention are shown inFIGS. 1b, 1 c and 3 b and may be made from one or more biocompatible,optically clear materials, for example silicone or the group ofcompounds known as acrylic polymers, such as polymethyl methacrylate(PMMA), polyhydroxymethyl methacrylate, or copolymers of silicone andmethylmethacrylate, collagen/acrylic blends, or other known materials.Optical body (12) has an anterior surface (120) in a spherical shape toprovide the prescribed optical correction. The posterior surface of thepreferred embodiment has a slightly smaller radius (127) than thecurvature of the haptic bodies (13) to assure there is no contact withthe natural lens at its apex (148) during accommodation of the eye wherethe natural lens radius is reduced (see FIGS. 1c and 1 g).

Turning to FIG. 4c, annular protruding surface (43) protrudes into thepupil of the eye such that the iris of the eye (42) interferes slightlyand provides a centering force to the lens. Once the lens is centered inthe pupil of the eye, the iris rides up the annular protruding surface(43), which may be slightly ramped or curved at the edge (44) to assureno trauma to the iris (42), and slides over the optical body as shown insequence in FIGS. 4a and 4 b.

For lenses with very high corrective power (see FIGS. 2a, b and c), asmaller radius of curvature is required and the optical body (22) may bestepped (21) to reduce the thickness of the lens such that it fitswithin the posterior chamber of the eye and does not substantiallyprotrude into the anterior chamber. In FIG. 1a, a similar centeringmeans exists with a positive lens (11) where an annular peripheral area(122) of the lens (11), that is sufficiently steep, protrudes into thepath of the iris such that the iris will place a centering force on thelens as it constricts and slides up and over the convex anterior surface(14).

FIG. 1a shows a lens (11) with two haptic bodies (13) that are thin andsubstantially uniform in thickness (129) (thickness preferably nogreater than about 0.15 mm) and are made from a flexible biocompatablematerial such that they can flex under very light loads in the directionof the optical axis (128). Now turning to FIG. 4c, the haptic bodies(47) have a diameter or diagonal measurement (L) from edge to edge suchthat they are smaller than the diameter of the periphery of theposterior chamber (C) of the eye in the area of the ciliary sulcus (48).When diagonal measurement (L) is less than the width of the posteriorchamber (C), the lens is allowed to float freely in the posteriorchamber. However, the lens (41) is still held loosely in the eye suchthat the lens does not grossly decenter. The annular protrudingsurface(s) (43) must be held such that they are entirely within thepupil of the eye when dilated to its maximum aperture (P). Should thelens (41) decenter such that the protruding annular surface (43) isbeyond the maximum aperture of the pupil (P), the protruding annularsurfaces (43) will act to decenter the lens rather than to center it.Haptics (47) restrict this motion and keep the annular protrudingsurface (43) inside the dilated pupil. A similar action occurs with thepositive lens (11) shown in FIG. 1a where the curvature of the lensitself protrudes (122) to receive a centering force applied by the irisas it constricts. Returning to FIG. 4c, the diameter of the outermostedges of the haptic(s) (L) is given by simultaneously meeting thefollowing inequalities:

L≧C−P+B

L≧C/2+P/2

L<C

where

L is the largest diameter of a circle that the outermost edges of thehaptic body(ies) will fit within;

C is the diameter of the eye at the ciliary sulcus;

P is the fully dilated diameter of the patient's pupil; and

B is the diameter of the annular protruding surface(s).

Should more than one annular protruding surface diameter (B) existwithin a single embodiment (such as shown in FIGS. 2a or 2 b), eachsurface is calculated individually using its particular diameter (B) andany one or any combination of these surfaces must satisfy the aboveinequalities.

For a positive lens (11), shown in FIG. 1a, diameter B is measured at apoint where the iris will contact the annular protruding surface withadequate force to center the lens; this is the diameter of the lensitself at an area (122) where the iris will contact it with adequateforce to center the lens.

The intraocular corrective lens of the present application must includea protruding surface which allows the iris to slide over it withoutrestricting the movement of the iris. It is this interaction between theprotruding surface and the iris which keeps the lens centered in theeye. The protruding surface may be a part of the optical body itself, asin FIG. 1a, or it may be adjacent to but not a part of the optical body,as in FIG. 1b. It is also possible, although not preferred, that theprotruding surface be wholly separate from the optic body. Theprotruding surfaces may be annular in shape and are generally sloped,curved or ramped at their edges in order to permit the iris to movecomfortably over them. The protruding surfaces may also be stepped asshown in FIGS. 2a, 2 b or 2 c. The height of the protruding surface isgenerally from about 0.25 to about 1.0 mm from the posterior surface ofthe lens. The optical body of the intraocular corrective lens, whenplaced in the eye, is located substantially in the posterior chamber ofthe eye behind the iris.

The structure of the optical body, which acts as the lens in the presentinvention, follows the requirements of standard optical theory. The lensmay have a concave or convex surface (positive or negative opticalpower). It may be torroidal, spherical or aspherical in shape. Thecurvature of the lens will depend on the optical correction required fora particular patient, keeping in mind that the lens will be usedtogether with the eye's natural lens. The precise structure of theoptical body may, in part, determine the structure of the protrudingsurfaces required to center the lens. The lens is generally made from aflexible, biocompatible transparent material. Hydrophilic materials andgas permeable materials are preferred. Examples of such materialsinclude, but are not limited to, silicones, silicone-methacrylatecopolymers, polymethyl methacrylate, polyhydroxyethyl methacrylate, andcollagen/acrylic blends. Mixtures or copolymers of those materials mayalso be used. The curvature of the optical body, and particularly theposterior surface of the optical body, relative to the curvature of thehaptic bodies of the lens, as described above, is chosen to maximize theability of the lens to float freely in the eye without interfering withthe eye's natural lens and consistent with the optical characteristicsrequired from the lens (optical body). The lens of the presentinvention, therefore, does not rest directly on the eye's natural lens.

One or more haptic bodies are included in the intraocular lens of thepresent invention. Examples of haptic structures which may be used areshown in FIG. 3. The haptics are made from the same types of materialsthat the optical body of the lens is made from. The haptics aregenerally substantially of uniform thickness and preferably have athickness of no greater than about 0.15 mm. The haptics are generallynot planar and, as discussed above, the radius of curvature of thehaptics taken together with the radius of curvature of the optical body,helps determine the ability of the lens to float freely in the eye. Itis preferred that the maximum diagonal haptic dimension of the lens (L)be from about 10.5 to about 11.5 mm. The haptic bodies should beflexible in the direction of the optical axis of the lens. The flexingof the haptic created by the natural dynamic action of the eyecirculates or assists in circulating the aqueous fluid of the eye.

What is claimed is:
 1. A phakic intraocular corrective lens having ananterior and a posterior side, comprising an optical body; a pluralityof haptic bodies attached to and extending outwardly from said opticalbody to a maximum diagonal haptic dimension of from about 10.5 to about11.5 mm, and having a thickness of no greater than about 0.15 mm; anannular protruding surface of such size, shape and position that, whenpositioned in the eye, it will contact the iris at one or more points asthe iris constricts to place a centering force on the lens, saidprotruding surface having a height above the posterior side of the lensof from about 0.25 to about 1 mm; said lens configured such that whenplaced in the eye, the optical body is located substantially in theposterior chamber of the eye behind the iris and is floating in theaqueous humor between the iris and the natural lens, and wherein saidintraocular lens does not include a means for permanent fixation in theeye.
 2. The phakic intraocular corrective lens according to claim 1wherein the optical body is free of openings between its anterior andposterior sides.
 3. The phakic intraocular corrective lens according toclaim 1 wherein the radius of curvature of the posterior surface of theoptical body is substantially equal to the radius of curvature of thehaptic bodies.
 4. The phakic intraocular corrective lens according toclaim 1 wherein the optical body has a negative curvature.
 5. The phakicintraocular corrective lens according to claim 1 wherein the protrudingsurface is of such size and shape that it allows the iris to slide overit without restricting the movement of the iris.
 6. The phakicintraocular corrective lens according to claim 5 wherein the protrudingsurface is sloped, curved or ramped at the portion of the surface whichcontacts the iris.
 7. The phakic intraocular corrective lens accordingto claim 6 which is made from an optically clear hydrophilicgas-permeable material.
 8. The phakic intraocular corrective lensaccording to claim 6 made from an optically clear material selected fromthe group consisting of silicones, silicon-methacrylate copolymers,polymethyl methacrylate, polyhydroxyethyl methacrylate,collagen/acrylate blends, and mixtures and copolymers thereof.
 9. Thephakic intraocular corrective lens according to claim 6 wherein thehaptic bodies are nonplanar, of substantially uniform thicknessthroughout their length, and are flexible in the direction of theoptical axis of the lens.